The present invention relates to a multiple jet hydrodemolition apparatus and method in which multiple hydrodemolition nozzles are operated to cover a greater area in a single pass than a unit with a single nozzle. The term hydrodemolition is sometimes referred to as hydromilling or hydroplaning.
Many concrete surfaces whether in parking lots, over bridges, on tunnel walls, building walls or any other concrete surface are frequently accompanied by heavy steel reinforcement. Once cracks in the concrete develop, road salts corrode the steel. This corrosion accelerates the destructive cycle of moisture, salt, freeze-thaw, corrosion, vibration and traffic. Conventional methods of repairing these concrete surfaces involves first the removal of the deteriorated concrete surface around and below the reinforcing steel bars. This removal allows placement of new concrete surface over the reinforcing steel.
Ordinarily concrete removal has been accomplished by jackhammers, but the use of jackhammers is time-consuming, and costly and makes it difficult to achieve complete removal of deteriorated concrete. In addition, the use of a jackhammer causes microcracking of the remaining concrete in surrounding areas. In order to improve the speed and efficiency of concrete removal from bridge decks, highways, substructures and parking garages and, at the same time, avoiding the problems caused by microcracking, contractors began using high-pressure water jets to remove the concrete. The use of high pressure water jets, termed hydrodemolition, involves moving an oscillating or rotating nozzle back and forth across a bed for a number of passes and then indexing or advancing a vehicle on which the bed and nozzle are supported to a next position where the process is repeated until a desired depth of concrete deck surface has been removed. The removal leaves clean reinforcing rod which has been descaled but otherwise undamaged and a rough textured concrete surface under the reinforcing rod which is ideal for bonding of new overlay. All deteriorated concrete is removed and entrained chlorides washed away. There is a greatly reduced noise and no vibration or dust.
The conventional equipment used in hydrodemolition has one nozzle, which runs over a guide bed and traverses a swath to be treated. After each pass the machine is indexed until a region has been impacted by one traversal. The vehicle is then reversed and the process repeated with the machine moving in indexes in reverse. Again once the swath has been covered the vehicle is moved forward in an indexed manner and traversals of the nozzle are repeated until the swath has been covered three times. Ordinarily three such passes are required to complete the hydrodemolition. Since the cost of a job is directly proportional to the time taken to accomplish it, there is a need for a faster more efficient method of applying hydrodemolition than that currently used. Some conventional equipment will complete a number of passes in a given position before being indexed forward where a like number of passes is then completed.
Accordingly, it is an object of the invention to provide an improved method and apparatus for applying hydrodemolition. It is a further object to provide a faster method of treating a surface with hydrodemolition than is currently in use.
According to the invention there is provided an apparatus for hydrodemolition having a movable vehicle, a fluid jet assembly having at least three nozzles, one behind the other, coupled to said vehicle and each oriented to direct a jet of fluid onto an underlying concrete surface, a bed coupled to the vehicle for guiding the nozzles back and forth transverse to a direction of movement of the vehicle, a fluid flow controller coupled to each of the nozzles from a source of high pressure fluid such that the fluid flow to each nozzle is independently controlled and means for moving the nozzles back and forth.
Preferably, the nozzles are one of rotatable and oscillatory and direct fluid at an angle to the vertical so that it can clean around reinforcing steel. Advantageously, the pressure of fluid supplied to each nozzle is independently controllable. Advantageously, the nozzles may be mounted at progressively lower positions, with respect to the subject concrete surface, such that, as layers of concrete are stripped away, the nozzles are maintained at an optimal distance from the subject concrete surface.
In another aspect of the invention there is provided a method of hydrodemolition which includes making a first transverse pass across a surface to be treated with a first fluid jet from a first fluid nozzle, and incrementing said first fluid nozzle forwardly and making transverse passes at each incremental position until a second nozzle reaches the position of the first transverse pass and then turning on the fluid to said second nozzle so that the second nozzle impacts the same region as did the first nozzle during the fist pass. The first and second nozzles make transverse passes and are incremented forward until a third nozzle reaches the position of the first transverse pass. Fluid to the third nozzle is then turned on so that the third nozzle impacts the same region as did the first nozzle during the first pass. Next the first, second and third nozzles are incremented repeatedly until the first fluid jet impacts on a last transverse pass after which the first nozzle is turned off. The second nozzle is incremented repeatedly until it reaches a position of the last transverse pass after which it is turned off. The third nozzle is incremented repeatedly until it reaches the position of the last transverse pass. After completing the last transverse pass the third nozzle is turned off.
In an alternate embodiment of the invention there is provided a method of hydrodemolition which includes making a first transverse pass across a surface to be treated with a first fluid jet from a first nozzle, and moving said first nozzle forward continuously and making transverse passes until a second nozzle reaches the position of the first transverse pass and then turning on the fluid to said second nozzle so that the second fluid jet impacts the same region as did the first fluid jet during the fist pass. The first and second nozzles move forward continuously and make transverse passes until a third nozzle reaches the position of the first transverse pass and then fluid to said third nozzle is turned on so that the third fluid jet impacts the same region as did the first fluid jet during the first pass. The first, second and third nozzles move forward continuously and make transverse passes until the first fluid jet impacts on a last transverse pass of the subject surface after which it is turned off. The second fluid jet moves forward continuously and makes transverse passes until it reaches a position of the last transverse pass of the subject surface after which it is turned off. The third fluid jet moves forward continuously and makes transverse passes until it reaches a position of the last transverse pass of the subject surface. After completing the last transverse pass the third nozzle is turned off.